Method and apparatus for directional association in a wireless communications system

ABSTRACT

A method of wireless communications is provided. The method includes transmitting, from the first device to the second device, at least one association request having a plurality of packets, each packet being respectively transmitted in a different direction; detecting an association response from the second device; and determining a preferred first device to second device direction of transmission based on the association response. An apparatus for performing the method is also disclosed.

CLAIM OF PRIORITY

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 61/113,602, entitled “METHOD AND APPARATUS FORCHANNEL ACCESS IN A WIRELESS COMMUNICATIONS SYSTEM”, filed Nov. 12,2008, and assigned Attorney Docket No. 090424P1, the disclosure of whichis hereby incorporated by reference herein.

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 61/164,422, entitled “METHOD AND APPARATUS FORCHANNEL ACCESS IN A WIRELESS COMMUNICATIONS SYSTEM”, filed Mar. 28,2009, and assigned Attorney Docket No. 090424P2, the disclosure of whichis hereby incorporated by reference herein.

BACKGROUND

I. Field of the Disclosure

This disclosure relates generally to wireless communications systemsand, more particularly, to a method and apparatus for directionalassociation in a wireless communications system.

II. Description of the Related Art

In one aspect of the related art, devices with a physical (PHY) layersupporting either single carrier or Orthogonal Frequency DivisionMultiplexing (OFDM) modulation modes may be used for millimeter wavecommunications, such as in a network adhering to the details asspecified by the Institute of Electrical and Electronic Engineers (IEEE)in its 802.15.3c standard. In this example, the PHY layer may beconfigured for millimeter wave communications in the spectrum of 57gigahertz (GHz) to 66 GHz and specifically, depending on the region, thePHY layer may be configured for communication in the range of 57 GHz to64 GHz in the United States and 59 GHz to 66 GHz in Japan.

To allow interoperability between devices or networks that supporteither OFDM or single-carrier modes, both modes further support a commonmode. Specifically, the common mode is a single-carrier base-rate modeemployed by both OFDM and single-carrier transceivers to facilitateco-existence and interoperability between different devices anddifferent networks. The common mode may be employed to provide beacons,transmit control and command information, and used as a base rate fordata packets.

A single-carrier transceiver in an 802.15.3c network typically employsat least one code generator to provide spreading of the form firstintroduced by Marcel J. E. Golay (referred to as Golay codes), to someor all fields of a transmitted data frame and to performmatched-filtering of a received Golay-coded signal. Complementary Golaycodes are sets of finite sequences of equal length such that a number ofpairs of identical elements with any given separation in one sequence isequal to the number of pairs of unlike elements having the sameseparation in the other sequences. S. Z. Budisin, “Efficient PulseCompressor for Golay Complementary Sequences,” Electronic Letters, 27,no. 3, pp. 219-220, Jan. 31, 1991, which is hereby incorporated byreference, shows a transmitter for generating Golay complementary codesas well as a Golay matched filter.

For low-power devices, it is advantageous for the common mode to employa Continuous Phase Modulated (CPM) signal having a constant envelope sothat power amplifiers can be operated at maximum output power withoutaffecting the spectrum of the filtered signal. Gaussian Minimum ShiftKeying (GMSK) is a form of continuous phase modulation having compactspectral occupancy by choosing a suitable bandwidth time product (BT)parameter in a Gaussian filter. The constant envelope makes GMSKcompatible with nonlinear power amplifier operation without theconcomitant spectral regrowth associated with non-constant envelopesignals.

Various techniques may be implemented to produce GMSK pulse shapes. Forexample, π/2-binary phase shift key (BPSK) modulation (orπ/2-differential BPSK) with a linearized GMSK pulse may be implemented,such as shown in I. Lakkis, J. Su, & S. Kato, “A Simple Coherent GMSKDemodulator”, IEEE Personal, Indoor and Mobile Radio Communications(PIMRC) 2001, which is incorporated by reference herein, for the commonmode.

SUMMARY

Aspects disclosed herein may be advantageous to systems employingmillimeter-wave wireless personal area networks (WPANs) such as definedby the IEEE802.15.3c protocol. However, the disclosure is not intendedto be limited to such systems, as other applications may benefit fromsimilar advantages.

According to an aspect of the disclosure, a method for associating afirst device with a second device is provided. The method includestransmitting, from the first device to the second device, at least oneassociation request comprising a plurality of packets, each packet beingrespectively transmitted in a different direction; detecting anassociation response from the second device; and determining a preferredfirst device to second device direction of transmission based on theassociation response.

According to another aspect of the disclosure, a wireless communicationsapparatus is provided. The apparatus includes means for transmitting toa device at least one association request comprising a plurality ofpackets, each packet being respectively transmitted in a differentdirection; means for detecting an association response from the device;and means for determining a preferred apparatus to device direction oftransmission based on the association response.

According to another aspect of the disclosure, a computer-programproduct for wireless communications is provided. The computer-programproduct includes a machine-readable medium with instructions executableto transmit, from the first device to the second device, at least oneassociation request comprising a plurality of packets, each packet beingrespectively transmitted in a different direction; detect an associationresponse from the second device; and determine a preferred first deviceto second device direction of transmission based on the associationresponse.

According to another aspect of the disclosure, an apparatus for wirelesscommunications is provided. The apparatus includes a processing systemconfigured to transmit to a device, at least one association requestcomprising a plurality of packets, each packet being respectivelytransmitted in a different direction; detect an association responsefrom the device; and determine a preferred apparatus to device directionof transmission based on the association response.

According to another aspect of the disclosure, an access terminal isprovided. The access terminal includes an antenna; and a processingsystem configured to transmit to a device, via the antenna, at least oneassociation request comprising a plurality of packets, each packet beingrespectively transmitted in a different direction; detect an associationresponse from the device; and determine a preferred access terminal todevice direction of transmission based on the association response.

According to another aspect of the disclosure, a method for associatinga first device with a second device is provided. The method includesacquiring a preferred second device to first device transmissiondirection; determining a preferred first device to second devicedirection of transmission based on the acquisition of the preferredsecond device to first device transmission direction; transmitting tothe second device at least one association request comprising at leastone packet from a plurality of packets generated by the first device,each packet being respectively transmittable in a different direction;and wherein the at least one packet comprises information related to thedetermined preferred first device to second device direction oftransmission.

According to another aspect of the disclosure, a apparatus for wirelesscommunications with another device is provided. The wirelesscommunications apparatus includes means for acquiring a preferred deviceto apparatus transmission direction; means for determining a preferredapparatus to device direction of transmission based on the acquisitionof the preferred device to apparatus transmission direction; and meansfor transmitting to the device at least one association requestcomprising at least one packet from a plurality of packets generated bythe apparatus, each packet being respectively transmittable in adifferent direction; wherein the at least one packet comprisesinformation related to the determined preferred apparatus to devicedirection of transmission.

According to another aspect of the disclosure, a computer-programproduct for wireless communications for associating a first device witha second device is provided. The computer-program product includes amachine-readable medium with instructions executable to acquire apreferred second device to first device transmission direction;determine a preferred first device to second device direction oftransmission based on the acquisition of the preferred second device tofirst device transmission direction; and transmit to the second deviceat least one association request comprising at least one packet from aplurality of packets generated by the first device, each packet beingrespectively transmittable in a different direction; wherein the atleast one packet comprises information related to the determinedpreferred first device to second device direction of transmission.

According to another aspect of the disclosure, an apparatus for wirelesscommunications with another device is provided. The apparatus includes aprocessing system configured to acquire a preferred device to apparatustransmission direction; determine a preferred apparatus to devicedirection of transmission based on the acquisition of the preferreddevice to apparatus transmission direction; and transmit to the deviceat least one association request comprising at least one packet from aplurality of packets generated by the apparatus, each packet beingrespectively transmittable in a different direction; wherein the atleast one packet comprises information related to the determinedpreferred apparatus to device direction of transmission.

According to another aspect of the disclosure, an access terminal forwireless communications with another device is provided. The accessterminal includes an antenna; and a processing system configured toacquire a preferred device to access terminal transmission direction;determine a preferred access terminal to device direction oftransmission based on the acquisition of the preferred device to accessterminal transmission direction; and transmit to the device, via theantenna, at least one association request comprising at least one packetfrom a plurality of packets generated by the access terminal, eachpacket being respectively transmittable in a different direction;wherein the at least one packet comprises information related to thedetermined preferred access terminal to device direction oftransmission.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Whereas some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following Detailed Description. The detaileddescription and drawings are merely illustrative of the disclosurerather than limiting, the scope of the disclosure being defined by theappended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a wireless network configured in accordance withan aspect of the disclosure;

FIG. 2 is a diagram of a superframe structure configured in accordancewith an aspect of the disclosure that is used in the wireless network ofFIG. 1;

FIG. 3 is a diagram of a frame/packet structure configured in accordancewith an aspect of the disclosure that is used in the superframestructure of FIG. 2;

FIG. 4 is a structure diagram of a preamble having various lengths inaccordance with an aspect of the disclosure;

FIG. 5 is a structure diagram of a superframe structure for use inproactive beamforming as configured in accordance with one aspect of thedisclosure;

FIGS. 6A and 6B are diagrams illustrating various antenna patterns thatmay be implemented on devices in the wireless network of FIG. 1 inaccordance with an aspect of the disclosure;

FIG. 7 is a block diagram of a superframe structure for a trainingsequence, configured in accordance with an aspect of the disclosure,used by a device in the wireless network of FIG. 1 to train otherdevices of interest;

FIG. 8 is a block diagram of a frame structure used during a generaltraining cycle in the training sequence of FIG. 7 as configured inaccordance with an aspect of the disclosure;

FIG. 9 is a timing diagram for an example cycle of the training sequenceof FIG. 7 as configured in accordance with an aspect of the disclosure;

FIG. 10 is a packet structure for a training packet used during thegeneral training cycle;

FIG. 11 is a frame structure for a feedback stage of the trainingsequence of FIG. 7 configured in an aspect of the disclosure;

FIG. 12 is a transmitted packet structure and timing description for adevice to detect the transmitted packet;

FIG. 13 is a transmitted packet structure and timing description for adevice to detect transmission by other devices;

FIG. 14 is a block diagram of a training request apparatus configured inaccordance with an aspect of the disclosure;

FIG. 15 is a block diagram of a receiver apparatus configured inaccordance with an aspect of the disclosure;

FIG. 16 is a block diagram of a channel time allocation apparatusconfigured in accordance with an aspect of the disclosure;

FIG. 17 is a block diagram of an association request apparatus forassociating a first device to a second device configured in accordancewith an aspect of the disclosure;

FIG. 18 is a block diagram of a preferred direction acquisitionapparatus configured in accordance with an aspect of the disclosure; and

FIG. 19 is a block diagram of a clear channel determination apparatusconfigured in accordance with an aspect of the disclosure.

FIG. 20 is a block diagram of a Golay-code circuitry configured inaccordance with one aspect of the disclosure;

FIGS. 21A and 21B are beamforming and superframe information elementsconfigured in accordance with one aspect of the disclosure; and,

FIG. 22 is a flow chart of a device with an omnidirectional receiveantenna configured in accordance with various aspects of the disclosure.

In accordance with common practice the various features illustrated inthe drawings may be simplified for clarity. Thus, the drawings may notdepict all of the components of a given apparatus (e.g., device) ormethod. In addition, like reference numerals may be used to denote likefeatures throughout the specification and figures.

DETAILED DESCRIPTION

Various aspects of the disclosure are described below. It should beapparent that the teachings herein may be embodied in a wide variety offorms and that any specific structure, function, or both being disclosedherein are merely representative. Based on the teachings herein oneskilled in the art should appreciate that an aspect disclosed herein maybe implemented independently of any other aspects and that two or moreof these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein.

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the disclosure. It should be understood, however, thatthe particular aspects shown and described herein are not intended tolimit the disclosure to any particular form, but rather, the disclosureis to cover all modifications, equivalents, and alternatives fallingwithin the scope of the disclosure as defined by the claims.

In one aspect of the disclosure, a dual-mode millimeter wave systememploying single-carrier modulation and OFDM is provided with asingle-carrier common signaling. The common mode is a single-carriermode used by both single-carrier and OFDM devices for beaconing,signaling, beamforming, and base-rate data communications.

Several aspects of a wireless network 100 will now be presented withreference to FIG. 1, which is a network formed in a manner that iscompatible with the IEEE 802.15.3c Personal Area Networks (PAN) standardand herein referred to as a piconet. The network 100 is a wireless adhoc data communication system that allows a number of independent datadevices such as a plurality of data devices (DEVs) 120 to communicatewith each other. Networks with functionality similar to the network 100are also referred to as a basic service set (BSS), or independent basicservice (IBSS) if the communication is between a pair of devices.

Each DEV of the plurality of DEVs 120 is a device that implements a MACand PHY interface to the wireless medium of the network 100. A devicewith functionality similar to the devices in the plurality of DEVs 120may be referred to as an access terminal, a user terminal, a mobilestation, a subscriber station, a station, a wireless device, a terminal,a node, or some other suitable terminology. The various conceptsdescribed throughout this disclosure are intended to apply to allsuitable wireless nodes regardless of their specific nomenclature.

Under IEEE 802.15.3c, one DEV will assume the role of a coordinator ofthe piconet. This coordinating DEV is referred to as a PicoNetCoordinator (PNC) and is illustrated in FIG. 1 as a PNC 110. Thus, thePNC includes the same device functionality of the plurality of otherdevices, but provides coordination for the network. For example, the PNC110 provides services such as basic timing for the network 100 using abeacon; and management of any Quality of Service (QoS) requirements,power-save modes, and network access control. A device with similarfunctionality as described for the PNC 110 in other systems may bereferred to as an access point, a base station, a base transceiverstation, a station, a terminal, a node, an access terminal acting as anaccess point, or some other suitable terminology. Both DEVs and PNCs maybe referred to as wireless nodes. In other words, a wireless node may bea DEV or a PNC.

The PNC 110 coordinates the communication between the various devices inthe network 100 using a structure referred as a superframe. Eachsuperframe is bounded based on time by beacon periods. The PNC 110 mayalso be coupled to a system controller 130 to communicate with othernetworks or other PNCs.

FIG. 2 illustrates a superframe 200 used for piconet timing in thenetwork 100. In general, a superframe is a basic time division structurecontaining a beacon period, a channel time allocation period and,optionally, a contention access period. The length of a superframe isalso known as the beacon interval (BI). In the superframe 200, a beaconperiod (BP) 210 is provided during which a PNC such as the PNC 110 sendsbeacon frames, as further described herein.

A Contention Access Period (CAP) 220 is used to communicate commands anddata either between the PNC 110 and a DEV in the plurality of DEVs 120in the network 100, or between any of the DEVs in the plurality of DEVs120 in the network 100. The access method for the CAP 220 can be basedon a slotted aloha or a carrier sense multiple access with collisionavoidance (CSMA/CA) protocol. The CAP 220 may not be included by the PNC110 in each superframe.

A Channel Time Allocation Period (CTAP) 220, which is based on a TimeDivision Multiple Access (TDMA) protocol, is provided by the PNC 110 toallocate time for the plurality of DEVs 120 to use the channels in thenetwork 100. Specifically, the CTAP is divided into one or more timeperiods, referred to as Channel Time Allocations (CTAs), that areallocated by the PNC 110 to pairs of devices; one pair of devices perCTA. Thus, the access mechanism for CTAs is TDMA-based.

During the beacon period, beacons using a set of antenna patterns,referred to as quasi-omni, or “Q-Omni” beacons, are first transmitted.Directional beacons-that is, beacons transmitted using higher antennagain in some direction(s) may additionally be transmitted during thebeacon period or in the CTAP between the PNC and one or multipledevices.

FIG. 3 is an example of a frame structure 300 that may be used for asingle carrier, OFDM or common mode frame. As used herein, the term“frame” may also be referred to as a “packet”, and these two termsshould be considered synonymous. The frame structure 300 includes apreamble 302, a header 340, and a packet payload 380. The common modeuses Golay codes for all three fields, i.e. for the preamble 302, theheader 340 and the packet payload 380. The common-mode signal uses Golayspreading codes with chip-level π/2-BPSK modulation to spread the datatherein. The header 340, which is a physical layer convergence protocol(PLCP) conforming header, and the packet payload 380, which is aphysical layer service data unit (PSDU), includes symbols spread with aGolay code pair of length-64. Various frame parameters, including, byway of example, but without limitation, the number of Golay-coderepetitions and the Golay-code lengths, may be adapted in accordancewith various aspects of the frame structure 300. In one aspect, Golaycodes employed in the preamble may be selected from length-128 orlength-256 Golay codes. Golay codes used for data spreading may compriselength-64 or length-128 Golay codes.

Referring back to FIG. 3, the preamble 302 includes a packet syncsequence field 310, a start frame delimiter (SFD) field 320, and achannel-estimation sequence field 330. The preamble 302 may be shortenedwhen higher data rates are used. For example, the default preamblelength may be set to 36 Golay codes for the common mode, which isassociated with a data rate on the order of 50 Mbps. For a data rate inthe order of 1.5 Gbps data rate, the preamble 302 may be shortened to 16Golay codes, and for data rates around 3 Gbps, the preamble 302 may befurther shortened to 8 Golay codes. The preamble 302 may also beswitched to a shorter preamble based upon either an implicit or explicitrequest from a device.

The packet sync sequence field 310 is a repetition of ones spread by oneof the length-128 complementary Golay codes (a^(i) ₁₂₈, b^(i) ₁₂₈) asrepresented by codes 312-1 to 312-n in FIG. 3. The SFD field 320comprises a specific code such as {−1} that is spread by one of thelength-128 complementary Golay codes (a^(i) ₁₂₈, b^(i) ₁₂₈), asrepresented by a code 322 in FIG. 3. The CES field 330 may be spreadusing a pair of length-256 complementary Golay codes (a^(i) ₂₅₆, b^(i)₂₅₆), as represented by codes 332 and 336, and may further comprise atleast one cyclic prefix, as represented by 334-1 and 338-1, such asa^(i) _(CP) or b^(i) _(CP) which are length-128 Golay codes, where CP isthe Cyclic Prefix or Postfix. A cyclic postfix for each of the codes 332and 336, such as a^(i) _(CP) or b^(i) _(CP) respectively, as representedby 334-2 and 338-2, respectively, are length-128 Golay codes.

In one aspect, the header 340 employs approximately a rate one-half ReedSolomon (RS) coding, whereas the packet payload 380 employs a rate-0.937RS coding, RS(255,239). The header 340 and the packet payload 380 may bebinary or complex-valued, and spread using length-64 complementary Golaycodes a^(i) ₆₄ and/or b^(i) ₆₄. Preferably, the header 340 should betransmitted in a more robust manner than the packet payload 380 tominimize packet error rate due to header error rate. For example, theheader 340 can be provided with 4 dB to 6 dB higher coding gain than thedata portion in the packet payload 380. The header rate may also beadapted in response to changes in the data rate. For example, for arange of data rates up to 1.5 Gbps, the header rate may be 400 Mbps. Fordata rates of 3 Gbps, the header rate may be 800 Mbps, and for a rangeof data rates up to 6 Gbps, the header rate may be set at 1.5 Gbps. Aconstant proportion of header rate may be maintained to a range of datarates. Thus, as the data rate is varied from one range to another, theheader rate may be adjusted to maintain a constant ratio of header rateto data-rate range. It is important to communicate the change in headerrate to each device in the plurality of DEVs 120 in the network 100.However, the current frame structure 300 in FIG. 3 used by all modes(i.e., single carrier, OFDM and common modes), do not include an abilityto do this.

FIG. 4 illustrates a preamble 400 in accordance with aspects of thedisclosure. Three preambles are defined as follows::

Long preamble: 8 sync symbols, 1 SFD symbol, 2 CES symbols;

Medium preamble: 4 sync symbols, 1 SFD symbol, 2 CES symbols; and

Short preamble: 2 sync symbols, 1 SFD symbol, 1 CES symbol;

where a symbol is a Golay code of length 512 and may be constructed fromeither a single or a pair of length 128 Golay codes.

During the beacon period, beacons with quasi-omni patterns, i.e.patterns that cover a relatively broad area of the region of space ofinterest, referred to as “Q-omni” beacons, are first transmitted.Directional beacons—that is, beacons transmitted using higher antennagain in some direction(s) may additionally be transmitted during thebeacon period or in the CTAP between PNC and one or more devices. Aunique preamble sequence set may be assigned to each piconet within thesame frequency channel, such as to improve frequency and spatial reuse:

s _(512,m) [n]=c _(4,m)[floor(n/128)]×u _(128,m) [n mod 128]n=0:511,

where the base sequences s_(512,m) occupy four non-overlappingfrequency-bin sets, and therefore, are orthogonal in both time andfrequency. The m^(th) base sequence occupies frequency bins m, m+4, m+8,m+12, . . . . In one aspect of the disclosure, modified Golay sequencesare generated from other Golay sequences, such as regular Golaycomplementary sequences, using time- or frequency-domain filtering toensure that only the used subcarriers are populated rather than theentire 512 subcarriers.

The term “regular Golay complementary sequences,” as used herein, anddenoted by a and b, may be generated using the following parameters:

1. A delay vector D of length M with distinct elements from the set 2 mwith m=0:M−1; and

2. A seed vector W of length M with elements from the QPSK constellation±1, ±j).

FIG. 20 illustrates a Golay-code circuitry 2000 that may be employedeither as a Golay code generator or a matched filter in some aspects ofthe disclosure. The Golay-code circuitry 2000 includes a sequence ofdelay elements 2002-1 to 2002-M configured for providing a determinedset of fixed delays D=[D(0), D(1), . . . , D(M−1)] to a first inputsignal. The delay profile provided by the delay elements 2002-1 to2002-M may be fixed, even when the Golay-code circuitry 2000 isconfigured to produce multiple Golay complementary code pairs. TheGolay-code circuitry 2000 also includes a sequence of adaptable seedvector insertion elements 2030-1 to 2030-M configured for multiplying asecond input signal by at least one of a plurality of different seedvectors W^(i)=[W(0), W(1), . . . , W(M−1)] to generate a plurality ofseed signals. The output from each of the sequence of adaptable seedvector insertion elements 2030-1 to 2030-M is fed into a first set ofcombiners 2010-1 to 2010-M to be combined with a respective output ofeach of the delay elements 2002-1 to 2002-M. In the implementation ofthe Golay-code circuitry 2000 as shown in FIG. 20, the output of eachseed vector insertion element 2030-1 to 2030-M is added to the output ofits respective delay elements 2002-1 to 2002-M by a respective one ofthe first set of combiners 2010-1 to 2010-M before the results thenbeing fed to the next stage. A second set of combiners 2020-1 to 2020-Mis configured for combining the delayed signals from the delay elements2002-1 to 2002-M with signals multiplied by the seed vector, where theseed signals are subtracted from the delay signals in the Golay-codecircuitry 2000.

Receivers implemented in accordance with certain aspects of thedisclosure may employ similar Golay-code generators to perform matchedfiltering of received signals so as to provide for such functionality aspacket or frame detection.

In one aspect, Golay codes (a1, a2, a3, and a4) may be generated bycombinations of Delay vectors (D1, D2, D3, and D3) and correspondingseed vectors (W1, W2, W3, and W4), as shown in the following table:

Delay and Seed Vectors for Golay sequences a1, a2, a3 & a4 D1 64 32 8 14 2 16 D2 64 32 8 1 4 2 16 D3 64 32 4 2 8 1 16 D4 64 32 4 2 8 1 16 W1 −1−j −1 −j −1 1 1 W2 −1 −1 1 +j 1 −j 1 W3 −1 −1 −1 −1 1 +j 1 W4 −1 −1 1 −11 −j 1 a or b 0 0 1 0

The first, second, and fourth sequences are type a, whereas the thirdsequence is type b. Preferred sequences are optimized to have minimumsidelobe levels as well as minimum cross-correlation.

In some aspects of the disclosure, a base rate may be employed for OFDMsignaling operations used for exchanging control frames and commandframes, associating to a piconet, beamforming, and other controlfunctions. The base rate is employed for achieving optimal range. In oneaspect, 336 data subcarriers per symbol may be employed withfrequency-domain spreading to achieve the base data rate. The 336subcarriers (subcarriers −176 to 176) may be divided into 4non-overlapping frequency bins, such as described with respect to thepreamble, and each set may assigned to one of a plurality of PNCsoperating in the same frequency band. For example, a first PNC may beallocated subcarriers −176, −172, −168, . . . , 176. A second PNC may beallocated subcarriers −-175, −171, −167, . . . , 173, and so on.Furthermore, each PNC may be configured for scrambling the data todistribute it over multiple subcarriers.

In IEEE 802.15.3, piconet timing is based on a super frame including abeacon period during which a PNC transmits beacon frames, a ContentionAccess Period (CAP) based on the CSMA/CA protocol, and a Channel TimeAllocation Period (CTAP), which is used for Management (MCTA) andregular CTAs, as further explained below.

During the beacon period, beacons with almost omnidirectional antennapatterns, referred to as quasi-omni, or “Q-omni” beacons, are firsttransmitted. Directional beacons—that is, beacons transmitted using someantenna gain in some direction(s) may additionally be transmitted duringthe beacon period or in the CTAP between two devices.

In order to reduce overhead when transmitting directional beacons, thepreamble may be shortened (e.g., the number of repetitions may bereduced) for higher antenna gains. For example, when an antenna gain of0-3 dB is provided, the beacons are transmitted using a default preamblecomprising eight modified Golay codes of length 512 and two CES symbols.For an antenna gain of 3-6 dB, the beacons employ a shortened preambleof four repetitions of same modified Golay code and two CES symbols. Foran antenna gain of 6-9 dB, the beacons transmit a shortened preamble oftwo repetitions of the same modified Golay code and 1 or 2 CES symbols.For antenna gains of 9 dB or more, the beacon preamble employs only onerepetition of the same Golay code and 1 CES symbol. If a header/beaconis used during beaconing or for data packets, the header-data spreadingfactor may be matched to the antenna gain.

Various aspects of the disclosure provide for a unified messagingprotocol that supports a wide range of antenna configurations,beamforming operations, and usage models. For example, antennaconfigurations may include directional or quasi-omni antennas,directional antenna patterns of a single antenna, diversity-switchedantennas, sectored antennas, beamforming antennas, phased antennaarrays, as well as other antenna configurations. Beamforming operationsmay include proactive beamforming, which is performed between a PNC anda device, and on-demand beamforming, which is performed between twodevices. Different usage models for both proactive beamforming andon-demand beamforming include per-packet beamforming from a PNC tomultiple devices and from at least one device to the PNC, transmissionsfrom a PNC to only one device, communications between devices, as wellas other usage models. Proactive beamforming is useful when the PNC isthe data source for one or multiple devices, and the PNC is configuredfor transmitting packets in different physical directions, each of whichcorresponding to a location of one or more devices for which packets aredestined.

In some aspects, the unified (SC/OFDM) messaging and beamformingprotocol is independent of the optimization approach (i.e., optimizingto find the best beam, sector or antenna weights), and antenna systemused in the devices in the wireless network 100. This allows forflexibility in the actual optimization approach employed. However, thetools enabling the beamforming should be defined. These tools shouldsupport all scenarios while enabling reduced latency, reduced overhead,and fast beamforming.

The following table shows four types of single-carrier beamformingpackets that may be employed by aspects of the disclosure.

Requirement Packet Preamble Length Header Rate Data Rate (M)andatory/Type (# 128 chips) (Mbps) (Mbps) (O)ptional I 36 50 50 M II 20 100 100 OIII 12 200 200 O IV 8 400 400 O

Since these are single-carrier packets transmitted using the commonmode, they can be decoded by both single-carrier and OFDM devices. Themajority of transmitted packets may have no body—just a preamble.

The different types of packets may be employed for different antennagains in such a way as to substantially equalize the total gain of thetransmissions, taking into consideration both coding gain and antennagain. For example, a Q-Omni transmission with 0˜3 dB antenna gain mayemploy type I packets. A directional transmission with 3˜6 dB antennagain may use type II packets. A directional transmission with 6˜9 dBantenna gain may use type III packets, and a directional transmissionwith 9˜12 dB antenna gain may uses type IV packets. In another aspect itis advantageous to transmit the beacon at the default rate in order toreduce the processing complexity at the devices and PNC.

FIG. 5 illustrates a superframe structure 500 that may be employed byvarious aspects of the disclosure to perform proactive beamforming. Thesuperframe structure 500 includes a beacon portion 550, a CAP 560 basedon the CSMA/CA protocol, and CTAP 580, which is used for Management(MCTA) and regular CTAs. The beacon portion 550 includes a Q-Omniportion and a directional portion 530. The directional portion 530includes the use of directional beacons that can be sent to differentdevices to convey more information.

The Q-Omni portion includes L1 transmissions in the superframe structure500, which is a plurality of Q-Omni beacons, as represented by Q-Omnibeacons 510-1 to 510-L1, each of which is separated by a respective MIFS(Minimum InterFrame Spacing which is a guard time), as represented by aplurality of MIFS 520-1 to 520-L1. In an aspect, L1 represents thenumber of Q-Omni directions that the PNC is able to supports For a PNCcapable of omnidirectional coverage—that is, a PNC having anomnidirectional-type antenna, L1=1. For a PNC with sectorized antennas,L1 would represent the number of sectors that the PNC is able tosupport. Similarly, when a PNC is provided with switching transmitdiversity antennas, L1 can represent the number of transmit antennas inthe PNC. Various approaches to the structure of the Q-omni beacon packetmay be used. Thus, for example, the L1 Q-omni beacons carry the samecontent, with the exception that each Q-omni beacon packet may have oneor more counters containing information about the index of the Q-omnibeacon packet and the total number of Q-omni beacons packets in theQ-omni portion.

In one aspect, the CAP 560 is divided into two portions, an associationCAP period 562 and a data communication CAP 572. The association CAP 562allows each of the devices to associate itself with the PNC. In oneaspect, the association CAP 562 is divided into a plurality of sub-CAPs(S-CAPs), which is represented by S-CAPs 562-1 to 562-L2, each followedby a respective Guard Time (GT), which is represented by GTs 564-1 to564-L2. L2 represents the maximum number of Q-omni receive directionscapable by the PNC, which may be different than L1, and thus, in oneaspect of the disclosure, during the association CAP period 562, the PNCwill listen in each of the L2 receive directions for an associationrequest from a device, i.e. during the th S-CAP the PNC will listen inthe eth receive direction, where I ranges from 1 to L2.

In an aspect where the channel is reciprocal (e.g., L1 equals L2),during the l^(th) S-CAP, where I can be any value from 1 to L1, the PNCreceives from the same antenna direction it used to transmit the l^(th)Q-Omni beacon. A channel is reciprocal between two devices, if the twodevices use the same antenna array for transmission and reception. Achannel is non-reciprocal if, for example, one of the devices usesdifferent antenna arrays for transmission and reception.

FIGS. 6A and 6B illustrate two example of antenna patterns 600 and 650,respectively. In FIG. 6A, a station 610 includes a plurality of antennadirections 602-1 to 602-L, with a k-th antenna direction 602-k.Similarly, in FIG. 6B, a station 660 includes a plurality of antennadirections 650-1 to 650-L with a k-th antenna direction 650-k. In oneaspect, each of the antenna directions may be part of a particularpattern with a resolution referred to herein as Q-Omni, sectors, beamsand High Resolution Beams (HRBs). Although the terms used herein referto antenna directions that are arbitrary in terms of actual resolution(e.g., area of coverage), a Q-Omni pattern may be thought to refer to anantenna pattern that covers a very broad area of a Region of Space ofInterest (RSI). In an aspect of the disclosure, a DEV is configured tocover the RSI with a minimal set of, possibly overlapping, Q-omniantenna directions. A sector may refer to a pattern that covers a broadarea using for example one fat beam or multiple narrower beams that canbe adjacent or not. In an aspect of the disclosure, sectors can overlap.Beams are a subset of High Resolution Beams (HRBs) that are of thehighest resolution level. In an aspect of the disclosure, adjustment ofthe resolution from beams to HRBs is achieved during a trackingoperation where a device monitors a set of HRBs around a given beam.

As discussed above, the CAP is based on a CSMA/CA protocol forcommunication between different devices (DEVs). When one of the DEVs inthe piconet is not omnidirection capable, any DEV desiring tocommunicate with that DEV during the CAP needs to know in whichdirection to transmit and receive. A non-omnidirection capable DEV canuse switched antennas, sectored antennas, and/or phased antenna arrays,referred to here as directional antennas, as further discussed herein.It should be noted that the information broadcast during the beacon canbe partitioned between Q-Omni and directional beacons in order tooptimize the Q-omni beacon.

As discussed previously, the PNC broadcasts a beacon in everysuperframe.

Each beacon contains all timing information about the superframe and,optionally, information about some or all of the DEVs that are membersof the piconet, including the beamforming capabilities of each DEV. Theinformation about the possible capabilities of some or all of the DEVswould preferably be communicated during the directional beacon sectionof the beacon period because directional beacons are transmitted athigher data rates and would better support the potentially large amountsof DEV capability information. The DEV beamforming capabilities areobtained by the PNC during association. A DEV beamforming capabilityincludes a number of coarse transmit and receive directions and numberof beamforming levels. For example, the number of coarse directionscould be a number of antennas for a DEV with switched antennas, a numberof sectors for a DEV with sectored antennas, or a number of coarsepatterns for a DEV with a phase antenna array. A phase antenna array cangenerate a set of patterns that might be overlapping; each patterncovers a part of the region of the space of interest.

A DEV needs to perform the following steps in order to associate (i.e.becomes a member of the piconet) with the PNC. First, the DEV searchesfor a beacon from the PNC. The DEV then detects at least one of theQ-omni beacons and acquires knowledge of the superframe timing, numberof Q-omni beacons, number and duration of S-CAPs, and, optionally, thepossible capabilities of each of the DEV members. In an aspect of thedisclosure, the DEV will acquire and track the best PNC directions bymeasuring a link quality indicator from all Q-omni beacons transmittedby the PNC. In one aspect of the disclosure, the Link quality indicator(LQI) is a metric of the quality of the received signal. Examples of LQIinclude but not limited to RSSI (Received Signal Strength Indicator),SNR (Signal to Noise Ratio), SNIR (Signal to Noise and InterferenceRatio), SIR (Signal to Interference Ratio), preamble detection, BER (BitError Rate), or PER (Packet Error Rate).

The DEV sends an association request to the PNC in one of the S-CAPs bysweeping over its set of L1 transmit directions, i.e. the DEV sends anassociation request comprising a set of L1 packets separated optionallyby a guard interval, where the mth packet (m=1, 2, . . . , L1) is sentin the DEV's transmit direction and where the packets contain the samecontent, with the exception that each packet may have in its header oneor more counters containing information about the total number ofpackets in the association request and the index of the current packet.Alternatively, each packet may have in its header the number ofremaining packets in the association request. Furthermore, eachassociation request (i.e., each packet in the association request) hasinformation to the PNC about its best transmit direction toward the DEV.This information is known to the DEV from beaconing. After sending theassociation request, the DEV then waits for an association response.

Upon detection of one of the packets that has been sent by the DEV, thePNC decodes information from the header about the remaining number ofpackets within the association request and is able to compute the timeleft until the end of the last packet, i.e., the time that it shouldwait before transmitting back the association response. The associationresponse from the PNC should inform the DEV about its best transmitdirection. Once an association response is received successfully by theDEV, the DEV and the PNC will be able to communicate through a set ofdirections: one from the DEV to the PNC and one from the PNC to the DEV,referred to a “working set of directions”, and will use this working setfor further communication in the S-CAP. Thus, in one aspect of thedisclosure, having a working set of directions means that the DEV knowswhich direction to use to transmit to the PNC and which S-CAP to target,and the PNC knows which transmit direction to use toward the DEV. Aworking set of directions does not necessarily mean the best set ofdirections between the PNC and the DEV. For example, a working directioncan be the first direction detected during the sweep with sufficientlink quality to allow the completion of the reception of the packet. Theworking set of directions can be determined to be the preferred or“best” set of directions by using a polling technique described below.Alternatively, upon successful detection of one of the packet within theassociation request, the PNC may monitor all remaining packets(transmitted in different directions by the DEV) in order to find thebest receive direction from the DEV, in which case the set of directionsis now a best set of directions. The PNC may acquire the DEVcapabilities (including beamforming capabilities) as part of theassociation request process or in a CTA allocated for furthercommunication between the PNC and the DEV.

If the DEV does not receive an association response from the PNC withina given time, than the DEV shall resend the association request bytrying one or more time in each of the S-CAPs until it successfullyreceives an association response from the PNC. In one aspect of thedisclosure, the PNC allocates only one S-CAP for association requests. ADEV can send an association request by sweeping over all of its transmitdirections as described above. Or, where the channel is symmetrical, theDEV can send the PNC the association request using the transmitdirection equivalent to the best receive direction from the PNC. Thisbest receive direction from the PNC is available to the DEV frommonitoring the beacon as described above. In another aspect of thedisclosure, the DEV can send an association request to the PNC in one ofthe DEV's transmit directions and wait to hear an acknowledgement fromthe PNC. If the DEV does not receive a response from the PNC, the DEVwill send another association request to the PNC in another one of theDEV's transmit direction, either in the same CAP or in the CAP ofanother superframe. Each association request will include informationcommon to the complete set of association requests, such as how manyassociation packets have been/are being sent in the set of associationrequests, and unique information of the particular association requestbeing transmitted, such as unique identification information of theactual association request.

The PNC may sweep over all of its receive directions to detect thepreamble of any packet within an association request transmitted by theDEV, whether that packet was sent as part of a set of packets in theassociation request or sent individually. Upon a successful receipt ofthe association request, the PNC will use the direction informationcontained therein to transmit information back to the DEV. Although thePNC may be able to decode the preamble of the packet based on the firstassociation request it is able to receive, the direction from which theDEV transmitted the association request may not be the most optimaldirection. Thus, the PNC can attempt to detect additional associationrequest packets to determine if subsequent association requests arebetter received.

The above-described procedure is a simplified version of a directionalassociation procedure, i.e. when PNC and/or DEV are not omnidirectioncapable. From the time-to-time, the PNC will poll each DEV to requestthat the DEV trains the PNC. This is necessary in order for the PNC totrack mobile devices. The training may be performed, for example, by theDEV sweeping over its set of transmit directions. The DEV itself doesnot need to be trained by the PNC because the DEV tracks the PNCdirection by monitoring the Q-omni beacons broadcast by the PNC, asdescribed above. In an aspect of the disclosure, if the channel betweenthe PNC and the DEV is reciprocal, than the DEV associates with the PNCwithout sweeping using the best pair of directions acquired during thebeacon period. If, for example, the PNC has four Q-omni beacons (i.e.,four directions in which it transmits Q-omni beacons) and the DEV hasthree receive directions, and the DEV has determined that the bestQ-omni beacon from which it receives transmissions from the PNC is thesecond Q-omni beacon and that its best receive direction is numberthree, than the DEV would use direction number three to send anassociation request in S-CAP number two to the PNC, with the associationrequest has information to the PNC about its best Q-omni direction, thatis number two. The PNC would than transmit the “association requestresponse” using transmit direction number two corresponding to itsreceive direction number two.

Assume that DEV-1 is interested in communicating with DEV-2, DEV-3, . .. . DEV-N. From the beacon, DEV-1 has learned everything about all otherDEVs members of the piconet. In order for DEV-1 to communicate withDEV-2 or DEV-3, . . . DEV-N efficiently in the CAP, since each DEV mayhave multiple directions of transmission or reception and each DEV doesnot know which direction to use when transmitting or receiving in theCAP, all of the DEVs that are not omnidirectional that are interested incommunicating with each other have to train each other.

In one aspect, the training sequence for DEV-1 is achieved as follows.Assume that DEV-j (j=1, 2, . . . , N) has MT(j) coarse transmitdirections and MR(j) coarse receive directions.

1. DEV-1 (or, alternatively, the PNC) computes the maximum number, NR,of coarse receive directions of DEV-2, DEV-3, . . . DEV-N, where:

NR=max(MR(2), MR(3), . . . , MR(N))

In an aspect of the disclosure, if the PNC is configured to compute themaximum number NR of coarse receive directions of DEV-2, DEV-3, . . . ,DEV-N, DEV-1 only needs to transmit the list of devices it is interestedin training (e.g., DEV-2, DEV-3, . . . , DEV-N) to the PNC.

2. DEV-1 requests a CTA from the PNC, informing the PNC that it wants totrain DEV-2, DEV-3, . . . , DEV-N. In an aspect of the disclosure,training equals locating the best pair of coarse (or fine) transmit andreceive directions between DEV-1 and each one of DEV-2, DEV-3, . . . ,DEV-N.

3. The CTA duration is computed by DEV-1 (or, alternatively, the PNC) asbeing at least NR×MT(1)×T, where T is the duration of the trainingpacket, including guard time. The CTA duration may also include aduration for a feedback stage. If the PNC computes the CTA duration,DEV-1 only needs to transmit the list of devices to be trained (e.g.,DEV-2, DEV-3, . . . , DEV-N).

4. The PNC allocates (i.e., grants) a CTA for DEV-1 for the training.

5. PNC broadcasts in the beacon the CTA allocation indicating that thesource is DEV-1, and the destination is either broadcast (if all devicesare to be trained) or a destination group including DEV-2, DEV-3, . . ., DEV-N (if only a subset of the devices are to be trained).

6. DEV-1 transmits the training packets during the allocated CTA, andDEV-2, DEV-3, . . . , DEV-N should receive the training during the CTA,as illustrated in FIG. 7.

It should be noted that, in one aspect of the disclosure, althoughcoarse directions are mentioned, the directions may also be finedirections, in which smaller separations are made between directions.

Each Q-Omni beacon may carry a beamforming information element 2140,such as shown in FIG. 21A to convey the structure of the beamformingbeacons to all devices listening to the PNC. Once a device decodes anyone of the Q-omni beacons during any superframe, it is capable ofunderstanding the entire beamforming cycle. In one aspect, thebeamforming information element 2140 includes a current Q-omni beacon IDfield 2150, a number of Q-omni beacons (e.g., the value L1 from theframe structure 500 of FIG. 5) field 2152, a length field 2154containing the number of octets in the information element, and anelement ID field 2156, which is the identifier of the informationelement. The current Q-omni beacon ID field 2150 contains a numberidentifying the number/position of the current Q-omni beacon beingtransmitted in the current superframe with respect to the number ofQ-omni beacons field 2152 in the superframe. A device, using the numbercontained in the current Q-omni beacon ID field 2150, will know whichQ-omni direction from which it heard the beacon.

FIG. 21B illustrates a superframe information element 2160 that istransmitted with the beamforming information element 2140, and includesa PNC address field 2162, a PNC response field 2164, a piconet mode2166, a maximum transmission power level 2168, a S-CAP duration field2170, a number of S-CAP periods field 2172, a CAP end time field 2174, asuperframe duration field 2176, and a time token 2178.

FIGS. 22A and 22B illustrate two approaches for a beamforming operationby devices in accordance with various aspect of the disclosure. FIG. 22Ais directed to a beamforming process 2200 of a device withomnidirectional receive capabilities. In step 2202 the omnidirectionaldevice only need to detect the Q-omni beacons of one superframe. If thedevice is not omnidirectional, the device needs to sweep over all itsreceived directions by listening to one or more superframes to detectthe beacon. Upon detection of the Q-omni beacons, the device stores aLink-Quality Factor (LQF) in step 2204 for each of the Q-omni beacons.Then, in step 2206, the device sorts the L LQFs, [LQF(1), . . . ,LQF(L)], and identifies the best PNC direction I corresponding to thehighest LQF:

l=arg{max[LQF(i)]}

i=1:L

In one aspect, the LQF is based on at least one of a signal strength, asignal to noise ratio, and a signal to noise and interference ratio. Inanother aspect, the LQF could also be based on any combination of theaforementioned factors.

In step 2208, the device associates itself with the PNC during thel^(th) CAP of the current superframe, and in step 2210 informs the PNCthat all further communications should occur with the PNC using itsl^(th) Q-omni direction. The device may still track the set of L bestdirections by monitoring the corresponding S-omni beacons every Qsuperframes. If a direction (e.g., the r^(th) S-omni direction) is foundwith a better LQF, the device may inform the PNC to transmit the nextpacket using the r^(th) S-omni direction by encoding it in the “NEXTDIRECTION” field in the PHY header.

On-demand beamforming may be performed between two devices, or between aPNC and one device. In one aspect of the disclosure, on-demandbeamforming is conducted in the CTA allocated to the link between twodevices. When a device is communicating with multiple devices, the samemessaging protocol as the proactive beamforming messaging protocol isused. In this case, the CTA will play the role of the beacon periodduring the beamforming phase, and will be used for data communicationthereafter. In the case where only two devices are communicating, sincethe CTA is a direct link between them, it is possible to employ a morecollaborative and interactive on-demand beamforming messaging protocol.

FIG. 7 illustrates a superframe structure 700 having a beacon 750, a CAP760, and a CTAP 780. The superframe structure 700 illustrates a trainingsequence where DEV-1 has requested an allocation for the purposes oftraining DEV-2, DEV-3, . . . , DEV-N, and the PNC has granted a CTA 784to DEV-1 to perform the training. During the CTA 784, DEV-1 trainsDEV-2, DEV-3, . . . , DEV-N using L cycles 730-1 to 730-L, whereL=MT(1), the total number of coarse transmit directions of DEV-1. Eachcycle is followed by a respective inter-frame spacing (IFS) (i.e., guardtime) 720-1 to 720-L. In one aspect, a feedback stage 730 is included,during which the results of the training is sent back to DEV-1 fromDEV-2, DEV-3, . . . , DEV-N, as further described herein.

In an aspect, during each cycle, DEV-1 transmits a number n of trainingpackets in a particular coarse transmit direction, where n=NR, thenumber of coarse receive directions of a DEV, from all devices DEV-2,DEV-3, . . . , DEV-N, that has the largest number of coarse receivedirections. For example, if DEV-4 has three (3) coarse receivedirections, which are equal to or larger than any of the number ofcoarse receive directions of the other DEVs in DEV-2, DEV-3, DEV-5 . . .DEV-N, then n=NR=3. Thus, DEV-1 will transmit three (3) trainingpackets. This repetitive transmission allows all DEVs DEV-2, DEV-3, . .. DEV-N to sweep through their coarse receive directions. In otherwords, DEV-1 has to transmit enough training packets during each cycleto enable all devices to attempt to detect a training packet over all oftheir respective coarse training directions.

FIG. 8 illustrates a series of transmissions 800 for a generalizedcycle, cycle #k, during the training by DEV-1 of DEV-2, DEV-3, . . . ,DEV-N. The illustration of the transmission of the n training packetsfor cycle #k is shown as transmissions 810-1 to 810-n. Each transmissionis followed by a respective IFS (i.e., guard time) 820-1 to 820-n. Inone aspect, each training packet is identical. As discussed above, thenumber n of training packets is equal to NR, the largest number oftraining directions of all the DEVs to be trained. Various approaches tothe structure of the training packet may be used. Thus, for example, ifthe training packets include the preamble portion only (i.e., no headeror payload portions), then the set of n training packets within a cyclecan be configured into a single large training packet. In one aspect ofthe disclosure, the total length the single large training packet wouldbe identical in length to the length of time it would take to transmitmultiple preamble-only packets, including the IFS or other inter-packetspacing. For example, to achieve the same length, the single largetraining packet can include more repetitive sequences to fill theportion normally taken by the IFS. Using a single large training packetapproach provide more flexibility to the devices being trained as thereis more time overall for detection and reception of the single largetraining packet. For example, a device being trained may sweep slower(i.e., extend the time the device listens in a particular direction) andhave better measurement accuracy because more samples of the preambleare bring captured. As another example, if a device can perform fastersweeps, then the device may complete training and enter into apower-saving mode for the rest of the single large training packettransmission.

FIG. 9 illustrates an example of one cycle of a training sequence for aDEV-1 that has six (6) transmit directions, a DEV-2 that has six (6)receive directions, and a DEV-3 that has two (2) receive directions. Asshown, during each cycle, the DEV-1 transmits a series of six trainingpackets #1 to #6, all in the same direction for DEV-1, one at a timeduring a period 902-1 to 902-6, respectively. Each of the other DEV's,DEV-2 and DEV-3, will listen for one of the training packets sent byDEV-1 using a different receive direction during each period. Forexample, as can be seen for DEV-2, during period 902-1, DEV-2 willlisten for training packet #1 from DEV-1 in a receive direction 1 of 6(RX ⅙) and DEV-3 will listen for training packet #1 from DEV-1 in areceive direction 1 of 2 (RX ½). In period 902-2, DEV-2 will listen fortraining packet #2 from DEV-1 in a receive direction 2 of 6 (RX 2/6) andDEV-3 will listen for training packet #2 from DEV-1 in a receivedirection 2 of 2 (RX 2/2). Presumably, DEV-3 will have heard trainingpacket #1 from DEV-1 during period 902-1, and identify that its bestreceive direction is RX ½. In period 902-3 through period 902-6, DEV-2will continue to listen for the training packets from DEV-1 in therespective receive directions indicated. However, DEV-3 may stop listenfor the training packets from DEV-1 as it has exhausted all the possiblereceive directions. During period 902-6, DEV-2 will hear training packet#6 from DEV-1 and thus identify its best receive direction for receivingtransmission from DEV-1 is RX 6/6. It should be noted that although thesweeping performed by each DEV-2 and DEV-3 are in a clockwise fashion,no specific pattern needs to be followed by any of the DEV's in terms ofdirection or sequence of sweeping of antenna directions. It should benoted that the best receive direction found by DEV-2 is only anillustration of the best found during a cycle and is not necessarily theoverall best receive direction as the search for the best has to be overall six cycles from DEV-1.

FIG. 10 illustrates a training packet structure 1000 configured inaccordance with an aspect of the disclosure that may be transmitted by atraining DEV, where the training packet structure 1000 simply includes apreamble portion without a frame body. If a frame body to be included itshould comprise the source address, i.e. the address of DEV-1 andoptionally the destination(s) addresses. The training packet structure1000 includes a packet sync (SYNC) sequence field 1010, a start framedelimiter (SFD) field 1040, and a channel-estimation sequence (CES)field 1080. In one aspect, the SYNC sequence field 1010 includes arepeating pattern of length 128 Golay sequences, while the CES field1080 includes a pair of complementary modified Golay sequences va 1082-1and vb 1082-2 produced from two length-512 complementary Golay sequencesa and b, which may be constructed from the length 128 Golay sequences.The SYNC sequence field 1010 is separated from the CES field 1080 by theSFD field 1040, which includes a Golay sequence pattern that breaks therepetition of the SYNC sequence field 1010. The SFD field is optional asthe CES can play a dual role. Optionally, a header portion may beincluded that includes at least the source address and, optionally, alldestination addresses. As discussed herein, the set of n trainingpackets within a cycle can be configured into a single large trainingpacket constructed, by way of example and not limitation, of a very longSYNC field, which in one aspect of the disclosure a repeating pattern ofthe length 128 Golay sequence m multiplied by n times.

As discussed above, returning to reference FIG. 7, during the feedbackstage 730, each of DEV-2, DEV-3, . . . , DEV-N informs DEV-1 of DEV-1'sbest coarse transmit direction and optionally its best coarse receivedirection. As there are N total devices DEV-1, DEV-2, DEV-3, . . . ,DEV-N, there are N-I feedbacks, one per DEV-j (j=2, . . . , N). A framesequence 1100 for achieving the feedback from each DEV is illustrated inFIG. 11, which includes a feedback portion shown as a DEV-2 feedback1110-2 to a DEV-N feedback 1110-N. Each feedback portion is followed byan IFS 1120-2 through 1120-N. In an aspect of the disclosure, whereDEV-1 is not omnidirectional in its reception, DEV-1 will have to listenin each of its possible receive directions for feedback from each of theDEV's. For example, DEV-1 will sweep through all possible receptiondirections while each of the DEV's DEV-2, DEV-3, . . . , DEV-N transmitstheir feedback to DEV-1. In an aspect of the disclosure, this method offeedback works optimally if the channel between DEV-1 and each of theDEVs is reciprocal, or if each of the DEVs is omni-capable ontransmission. If the channel between DEV-1 to any DEV is reciprocal, thebest direction from DEV-1 to that DEV will be used to provide feedbackfrom that DEV to DEV-1. In the case where the DEVs are not omni-capableon transmission or if the channel is not reciprocal, it is preferablefor DEV-1 to train each of DEV-2, DEV-3, . . .DEV-N individually. In anaspect of the disclosure, for example, a training session between DEV1-1and DEV-2 would include a training sweep from DEV-1 to DEV-2 in L1cycles (L1 is the number of DEV-1 transmit directions) followed by atraining sweeping from DEV2- to DEV-1 in L2 cycles (L2 is the number ofDEV-2 transmit directions) followed by feedback in a sweep from DEV-1 toDEV-2 followed by a feedback from DEV-2 to DEV-1. It should be notedthat one of the feedbacks can be integrated with the sweep training.Various approaches to the feeding back may be used. Thus, for example,if the channel is reciprocal and DEV-1 has trained DEV-2 and DEV-3, thenit might not be necessary for DEV-2 and DEV-3 to train back DEV-1 sincethe path from DEV-1 to DEV-2 is the same as the path from DEV-2 back toDEV-1, and the path from DEV-1 to DEV-3 is the same as the path fromDEV-3 back to DEV-1. Alternatively, if every device trains all otherdevices in the list, then the feedback stage can be omitted if thechannel is reciprocal.

At the end of the training sequence, each DEV from DEV-2, DEV-3, . . . ,DEV-N will have determined a respective best transmit coarse directionfrom DEV-1 and its own best coarse receive direction. In other words, atthe end of the training sequence, each DEV from DEV-2, DEV-3, . . .,DEV-N can identify the best coarse direction from which DEV-1 shouldtransmit, as well as the best coarse direction from which the particularDEV should listen (i.e., receive the transmission).

After DEV-1 has performed its training, the other DEVs (DEV-2, DEV-3, .. . , DEV-N) will request their own CTA from the PNC for the sametraining purposes. At the end of all training, each pair of DEVs (DEV-1,DEV-2, DEV-3, . . . , DEV-N) will have determined the best pair ofcoarse directions in both forward and reverse links.

The result of the training is useful in the transmission of informationbetween each DEV. This is particularly applicable to the CAP in oneaspect of the disclosure. Assume DEV-1 wants to transmit a packet toDEV-2 during a particular CAP. DEV-1 knows which direction to use totransmit to DEV-2. However, DEV-2 does not know which DEV istransmitting and therefore cannot direct its antenna in the rightdirection. To address this, in one aspect DEV-2 listens for a shortperiod of time in each of its receive direction. In one aspect, theshort period of time should be long enough to detect the presence of apreamble, such as the length of time to perform a clear channelassessment (CCA), for example.

As illustrated in FIG. 12, DEV-2 will continue to switch from one coarsereceive direction to another (i.e., sweep through some or all coarsereceive directions in each cycle) from coarse receive direction #1 to#P, where P=MR(2), the number of possible coarse receive directions ofDEV-2, until it detects the presence of a preamble 1220 from a packet1200 transmitted from DEV-1. This is illustrated by 1230-1 to 1230-P foreach cycle. It should be noted that DEV-2 might sweep over only a subsetof its coarse receive directions corresponding to receive directionsfrom potential sources, i.e. a sweep cycle consists of only a subset ofthe overall receive directions. For example if DEV-2 has done trainingwith only DEV-1 and DEV-3, than DEV-2 might continuously (i.e., multiplecycles) switch between only two coarse receive directions (per cycle)corresponding to best receive directions from DEV-1 and DEV-3 until itdetects the preamble or it times out. Once the preamble 1220 isdetected, DEV-2 does not need to try the other coarse directions.However, the detection of a preamble does not mean that DEV-2 hasacquired its best receive direction. The detection only means that DEV-2has found a receive direction that minimally allows it to receive thepacket. This receive direction is referred to as a working receivedirection. As discussed herein, a working direction can be the firstdirection detected during the sweep with sufficient link quality toallow the completion of the reception of the packet. In one aspect ofthe disclosure, the transmitting DEV (e.g., DEV-1) can incorporate thebest receive direction of DEV-2 in a header 1240 of the packet 1200. Inanther aspect, as both DEV-1 and DEV-2 have determined the best pairs oftransmit and receive coarse directions for each other during thetraining period, DEV-2 should be able to determine the best coarsereceive direction once it has determined the DEV that is trying to sendit the packet, which in this case is DEV-1. Either way, once DEV-2decodes the header of the packet sent by DEV-1, it knows its bestreceive direction and can switch to that direction to receive thepacket.

A DEV wanting to transmit a packet in the CAP can use the samemulti-cycle sweeping method to sense whether the medium is idle or ifanother transmission in the medium is possible. In an aspect of thedisclosure, if DEV-2 wants to transmit a packet to another DEV, DEV-2may first sense and measure energy by sweeping over differentdirections. As illustrated in FIG. 13, during a transmission period 1300of a packet with a preamble portion 1320 and a header/payload portion1340, if DEV-2 senses that the medium is idle (i.e., either no preambleis detected or the maximum detected energy is below a given threshold),then it may transmit the packet to the desired DEV. If, on the otherhand, DEV-2 determines that the medium is busy it will back off andrestart the sensing again at a later time. DEV-2 will continue to switchfrom one coarse receive direction to another (i.e., sweep through someor all coarse receive directions per cycle) from coarse receivedirections in the range #1 to #P, where P=MR(2), the number of possiblecoarse receive directions of DEV-2, until it times out or detects thepresence of energy as illustrated by 1330-1 to 1330-P. In another aspectof the disclosure, DEV-2 may sense the medium in only two directions,i.e., DEV-2's receive direction from the target DEV and a receivedirection corresponding to DEV-2's transmit direction. If DEV-2 sensesno preamble or energy in these two directions, it might transmit apacket to the target DEV in which case two other devices might becommunicating at the same time in another set of almost non-interferingdirections therefore achieving spatial reuse.

In one aspect of the disclosure, devices will communicate with otherover logical channels. A logical channel is a non-dedicatedcommunication path within a physical frequency channel between two ormore devices. Therefore, in a physical frequency channel, multiplelogical channels can exist, which means that multiple simultaneoustransmissions can occur. A logical channel is considered to be availablebetween a first device and a second device if the transmission directionfrom the first device to the second device causes no interference oracceptable interference to other active logical channels (i.e. operatingat the current transmission time). As an example of logical channels, adevice DEV-1 can transmit to another device DEV-2 in the horizontal beamdirection and DEV-3 can transmit to DEV-4 in the vertical beam directionat the same time. It should be obvious that the use of multiple logicalchannels enable spatial reuse.

FIG. 14 illustrates a training apparatus 1400 that may be used withvarious aspects of the disclosure, the training apparatus 1400 includingchannel time allocation (CTA) module 1402 for transmitting a channeltime allocation request from a first device to a second device, whereinthe channel time allocation request comprises a list of devices to betrained by the first device; CTA grant reception module 1404 thatreceives a channel time allocation granted by the second device; and atraining packet transmission module 1406 that transmits, from the firstdevice, at least one training packet to at least one device in the listof devices to be trained during the channel time allocation granted bythe second device.

FIG. 15 illustrates a receiver apparatus 1500 that may be used withvarious aspects of the disclosure, the receiver apparatus 1500 includinga preamble detection module 1502 that detect at least a portion of apreamble of a packet transmitted by a first device by sweeping over aplurality of receive directions; a preferred reception direction module1504 that completes the reception of the packet based on a preferredreceive direction that was established during a training session withthe first device; and a packet decoder module 1506 that receives anddecodes a header of the packet based on a first receive direction toidentify that the first device had transmitted the packet.

FIG. 16 illustrates a channel time allocation apparatus 1600 that may beused with various aspects of the disclosure, the channel time allocationapparatus 1600 including a CTA request reception module 1602 thatreceives, at a first device, a channel allocation request from a seconddevice, wherein the request comprises a list of devices to be trained bythe second device; and a beacon transmission module 1604 that transmitsa beacon from the first device, the beacon comprising a channelallocation for the second device based on the channel allocationrequest.

FIG. 17 illustrates an association request apparatus 1700 that may beused with various aspects of the disclosure for associating a firstdevice with a second device, the association request transmissionapparatus 1700 including an association request transmission module 1702that transmits, from the first device to the second device, at least oneassociation request including a plurality of packets, each packet beingrespectively transmitted in a different direction; an associationresponse detection module 1704 that detects an association response fromthe second device; and a preferred transmission direction module 1706that determines a preferred first device to second device direction oftransmission based on the association response.

FIG. 18 illustrates an association request apparatus 1800 that may beused with various aspects of the disclosure for associating a firstdevice with a second device, the association request apparatus 1800including a preferred second device to first device transmissiondirection acquisition module 1802 that acquires a preferred seconddevice to first device transmission direction; a preferred transmissiondirection determination module 1804 that determines a preferred firstdevice to second device direction of transmission based on theacquisition of the preferred second device to first device transmissiondirection; and an association request transmission module 1806 thattransmits to the second device at least one association requestcomprising at least one packet from a plurality of packets generated bythe first device, each packet being respectively transmittable in adifferent direction; wherein the at least one packet comprisesinformation related to the determined preferred first device to seconddevice direction of transmission.

FIG. 19 illustrates a channel assessment apparatus 1900 that may be usedwith various aspects of the disclosure, the channel assessment apparatus1900 including a clear channel determination module 1902 that determineswhether a logical channel is available for transmission by sweeping overa plurality of receive directions; and a data transmission module 1904that transmits data if the logical channel is available.

Various aspects described herein may be implemented as a method,apparatus, or article of manufacture using standard programming and/orengineering techniques. The term “article of manufacture” as used hereinis intended to encompass a computer program accessible from anycomputer-readable device, carrier, or media. For example, computerreadable media may include, but are not limited to, magnetic storagedevices, optical disks, digital versatile disk, smart cards, and flashmemory devices.

The disclosure is not intended to be limited to the preferred aspects.Furthermore, those skilled in the art should recognize that the methodand apparatus aspects described herein may be implemented in a varietyof ways, including implementations in hardware, software, firmware, orvarious combinations thereof. Examples of such hardware may includeASICs, Field Programmable Gate Arrays, general-purpose processors, DSPs,and/or other circuitry. Software and/or firmware implementations of thedisclosure may be implemented via any combination of programminglanguages, including Java, C, C++, Matlab™, Verilog, VHDL, and/orprocessor specific machine and assembly languages.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, processors, means, circuits, and algorithmsteps described in connection with the aspects disclosed herein may beimplemented as electronic hardware (e.g., a digital implementation, ananalog implementation, or a combination of the two, which may bedesigned using source coding or some other technique), various forms ofprogram or design code incorporating instructions (which may be referredto herein, for convenience, as “software” or a “software module”), orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implementedwithin or performed by an integrated circuit (“IC”), an access terminal,or an access point. The IC may comprise a general purpose processor, adigital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, electrical components, optical components,mechanical components, or any combination thereof designed to performthe functions described herein, and may execute codes or instructionsthat reside within the IC, outside of the IC, or both. A general purposeprocessor may be a microprocessor, but in the alternative, the processormay be any conventional processor, controller, microcontroller, or statemachine. A processor may also be implemented as a combination ofcomputing devices, e.g., a combination of a DSP and a microprocessor, aplurality of microprocessors, one or more microprocessors in conjunctionwith a DSP core, or any other such configuration.

The method and system aspects described herein merely illustrateparticular aspects of the disclosure. It should be appreciated thatthose skilled in the art will be able to devise various arrangements,which, although not explicitly described or shown herein, embody theprinciples of the disclosure and are included within its scope.Furthermore, all examples and conditional language recited herein areintended to be only for pedagogical purposes to aid the reader inunderstanding the principles of the disclosure. This disclosure and itsassociated references are to be construed as being without limitation tosuch specifically recited examples and conditions. Moreover, allstatements herein reciting principles, aspects, and aspects of thedisclosure, as well as specific examples thereof, are intended toencompass both structural and functional equivalents thereof.Additionally, it is intended that such equivalents include bothcurrently known equivalents as well as equivalents developed in thefuture, i.e., any elements developed that perform the same function,regardless of structure.

It should be appreciated by those skilled in the art that the blockdiagrams herein represent conceptual views of illustrative circuitry,algorithms, and functional steps embodying principles of the disclosure.Similarly, it should be appreciated that any flow charts, flow diagrams,signal diagrams, system diagrams, codes, and the like represent variousprocesses that may be substantially represented in computer-readablemedium and so executed by a computer or processor, whether or not suchcomputer or processor is explicitly shown.

The previous description is provided to enable any person skilled in theart to understand fully the full scope of the disclosure. Modificationsto the various configurations disclosed herein will be readily apparentto those skilled in the art. Thus, the claims are not intended to belimited to the various aspects of the disclosure described herein, butis to be accorded the full scope consistent with the language of claims,wherein reference to an element in the singular is not intended to mean“one and only one” unless specifically so stated, but rather “one ormore.” Further, the phrase “at least one of a, b and c” as used in theclaims should be interpreted as a claim directed towards a, b or c, orany combination thereof. Unless specifically stated otherwise, the terms“some” or “at least one” refer to one or more elements. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. No claim element is to be construed under the provisions of35 U.S.C. §112, sixth paragraph, unless the element is expressly recitedusing the phrase “means for” or, in the case of a method claim, theelement is recited using the phrase “step for.”

1. A method for associating a first device with a second device comprising: transmitting, from the first device to the second device, at least one association request comprising a plurality of packets, each packet being respectively transmitted in a different direction; detecting an association response from the second device; and determining a preferred first device to second device direction of transmission based on the association response.
 2. The method of claim 1, wherein the at least one association request is transmitted during a specific period of time allocated by the second device to receive association requests from other devices.
 3. The method of claim 1, wherein the at least one association request comprises a preferred second device to first device transmission direction.
 4. The method of claim 1, wherein the detection comprises attempting to detect the association response from the second device after the transmission of each packet in the plurality of packets.
 5. The method of claim 1, wherein the transmission comprises transmitting all packets in the plurality of packets within the at least one association request before attempting to detect the association response from the second device.
 6. The method of claim 1, wherein the association response comprises the preferred first device to second device transmission direction.
 7. The method of claim 1, wherein each packet comprises a length of transmission indicator.
 8. The method of claim 7, wherein the length of transmission indicator comprises a count.
 9. The method of claim 1, wherein each packet comprises a packet sequence indicator.
 10. An apparatus for wireless communications comprising: means for transmitting to a device at least one association request comprising a plurality of packets, each packet being respectively transmitted in a different direction; means for detecting an association response from the device; and means for determining a preferred apparatus to device direction of transmission based on the association response.
 11. The apparatus of claim 10, wherein the at least one association request is transmitted during a specific period of time allocated by the device to receive association requests from other devices.
 12. The apparatus of claim 10, wherein the at least one association request comprises a preferred device to apparatus transmission direction.
 13. The apparatus of claim 10, wherein the detecting means is configured to attempt to detect the association response from the device after the transmission of each packet in the plurality of packets.
 14. The apparatus of claim 10, wherein the transmitting means is configured to transmit all packets in the plurality if packets within the at least one association request before attempting to detect the association response from the device.
 15. The apparatus of claim 10, wherein the association response comprises the preferred apparatus to device transmission direction.
 16. The apparatus of claim 10, wherein each packet comprises a length of transmission indicator.
 17. The apparatus of claim 16, wherein the length of transmission indicator comprises a count.
 18. The apparatus of claim 10, wherein each packet comprises a packet sequence indicator.
 19. A computer-program product for wireless communications comprising: a machine-readable medium comprising instructions executable to: transmit, from the first device to the second device, at least one association request comprising a plurality of packets, each packet being respectively transmitted in a different direction; detect an association response from the second device; and determine a preferred first device to second device direction of transmission based on the association response.
 20. An apparatus for wireless communications comprising: a processing system configured to: transmit to a device, at least one association request comprising a plurality of packets, each packet being respectively transmitted in a different direction; detect an association response from the device; and determine a preferred apparatus to device direction of transmission based on the association response.
 21. The apparatus of claim 20, wherein the at least one association request is transmitted during a specific period of time allocated by the device to receive association requests from other devices.
 22. The apparatus of claim 20, wherein the at least one association request comprises a preferred device to apparatus transmission direction.
 23. The apparatus of claim 20, wherein the processing system is further configured to attempt to detect the association response from the device after the transmission of each packet in the plurality of packets.
 24. The apparatus of claim 20, wherein the processing system is further configured to transmit all packets in the plurality if packets within the at least one association request before attempting to detect the association response from the device.
 25. The apparatus of claim 20, wherein the association response comprises the preferred apparatus to device transmission direction.
 26. The apparatus of claim 20, wherein each packet comprises a length of transmission indicator.
 27. The apparatus of claim 26, wherein the length of transmission indicator comprises a count.
 28. The apparatus of claim 20, wherein each packet comprises a packet sequence indicator.
 29. An access terminal comprising: an antenna; and a processing system configured to: transmit to a device, via the antenna, at least one association request comprising a plurality of packets, each packet being respectively transmitted in a different direction; detect an association response from the device; and determine a preferred access terminal to device direction of transmission based on the association response.
 30. A method for associating a first device with a second device comprising: acquiring a preferred second device to first device transmission direction; determining a preferred first device to second device direction of transmission based on the acquisition of the preferred second device to first device transmission direction; and transmitting to the second device at least one association request comprising at least one packet from a plurality of packets generated by the first device, each packet being respectively transmittable in a different direction; wherein the at least one packet comprises information related to the determined preferred first device to second device direction of transmission.
 31. The method of claim 30, wherein the acquisition comprises sweeping a set of receive directions by the first device to detect a transmission from the second device.
 32. The method of claim 31, wherein the transmission from the second device comprises a beacon.
 33. The method of claim 32, wherein the beacon was transmitted using a plurality of packets, at least two packets being transmitted in different directions.
 34. The method of claim 30, wherein the at least one association request is transmitted during a specific period of time allocated by the second device to receive association requests from other devices.
 35. The method of claim 30, wherein a first packet from the plurality of packets from the at least one association request is transmitted during a specific period of time allocated by the second device to receive association requests from other devices.
 36. The method of claim 30, wherein a first packet from the plurality of packets from the at least one association request is transmitted using the determined preferred first device to second device transmission direction.
 37. The method of claim 30, further comprising determining whether an association response has been sent from the second device after the transmission of each of the packets in the plurality of packets.
 38. The method of claim 30, wherein each packet comprises a length of transmission indicator.
 39. The method of claim 38, wherein the length of transmission indicator comprises a count.
 40. An apparatus for wireless communications with another device comprising: means for acquiring a preferred device to apparatus transmission direction; means for determining a preferred apparatus to device direction of transmission based on the acquisition of the preferred device to apparatus transmission direction; and means for transmitting to the device at least one association request comprising at least one packet from a plurality of packets generated by the apparatus, each packet being respectively transmittable in a different direction; wherein the at least one packet comprises information related to the determined preferred apparatus to device direction of transmission.
 41. The apparatus of claim 40, wherein the acquisition comprises sweeping a set of receive directions to detect a transmission from the device.
 42. The apparatus of claim 41, wherein the transmission from the device comprises a beacon.
 43. The apparatus of claim 42, wherein the beacon was transmitted using a plurality of packets, at least two packets being transmitted in different directions.
 44. The apparatus of claim 40, wherein the at least one association request is transmitted during a specific period of time allocated by the device to receive association requests from other devices.
 45. The apparatus of claim 40, wherein a first packet from the plurality of packets from the at least one association request is transmitted during a specific period of time allocated by the device to receive association requests from other devices.
 46. The apparatus of claim 40, wherein a first packet from the plurality of packets from the at least one association request is transmitted using the determined preferred apparatus to device transmission direction.
 47. The apparatus of claim 40, further comprising means for determining whether an association response has been received from the device after the transmission of each of the packets in the plurality of packets.
 48. The apparatus of claim 40, wherein each packet comprises a length of transmission indicator.
 49. The apparatus of claim 48, wherein the length of transmission indicator comprises a count.
 50. A computer-program product for wireless communications for associating a first device with a second device comprising: a machine-readable medium comprising instructions executable to: acquire a preferred second device to first device transmission direction; determine a preferred first device to second device direction of transmission based on the acquisition of the preferred second device to first device transmission direction; and transmit to the second device at least one association request comprising at least one packet from a plurality of packets generated by the first device, each packet being respectively transmittable in a different direction; wherein the at least one packet comprises information related to the determined preferred first device to second device direction of transmission.
 51. An apparatus for wireless communications with another device comprising: a processing system configured to: acquire a preferred device to apparatus transmission direction; determine a preferred apparatus to device direction of transmission based on the acquisition of the preferred device to apparatus transmission direction; and transmit to the device at least one association request comprising at least one packet from a plurality of packets generated by the apparatus, each packet being respectively transmittable in a different direction; wherein the at least one packet comprises information related to the determined preferred apparatus to device direction of transmission.
 52. The apparatus of claim 51, wherein the acquisition comprises sweeping a set of receive directions to detect a transmission from the device.
 53. The apparatus of claim 52, wherein the transmission from the device comprises a beacon.
 54. The apparatus of claim 53, wherein the beacon was transmitted using a plurality of packets, at least two packets being transmitted in different directions.
 55. The apparatus of claim 51, wherein the at least one association request is transmitted during a specific period of time allocated by the device to receive association requests from other devices.
 56. The apparatus of claim 51, wherein a first packet from the plurality of packets from the at least one association request is transmitted during a specific period of time allocated by the device to receive association requests from other devices.
 57. The apparatus of claim 51, wherein a first packet from the plurality of packets from the at least one association request is transmitted using the determined preferred apparatus to device transmission direction.
 58. The apparatus of claim 51, wherein the processing system is further configured to determine whether an association response has been received from the device by the apparatus after the transmission of each of the packets in the plurality of packets.
 59. The apparatus of claim 51, wherein each packet comprises a length of transmission indicator.
 60. The apparatus of claim 59, wherein the length of transmission indicator comprises a count.
 61. An access terminal for wireless communications with another device comprising: an antenna; and a processing system configured to: acquire a preferred device to access terminal transmission direction; determine a preferred wireless node to device direction of transmission based on the acquisition of the preferred device to access terminal transmission direction; and transmit to the device, via the antenna, at least one association request comprising at least one packet from a plurality of packets generated by the access terminal, each packet being respectively transmittable in a different direction; wherein the at least one packet comprises information related to the determined preferred access terminal to device direction of transmission. 